1. Field of the Invention
This invention relates to circuit breaker and more particularly to extinguishing arcs generated during high current interruption through a terminal assembly that improves arc gas discharge.
2. Background Information
The current interruption capability of air circuit breakers is dependent in part upon their ability to extinguish the arc that is generated when the circuit breaker main contacts open. Even though the contacts separate, current continues to flow through the ionized gases formed by vaporization of the contacts and surrounding materials. The arc is extinguished through transfer to a set of stacked metal plates in an arc chute that break the arc into a series of arcs, thereby raising the electrical resistance of the arc with a commensurate increase in arc voltage and a reduction in arc current. The arc is also cooled by the flow of the arc gases induced by venting and through vaporization of the metal arc plates and surrounding materials. In the typical circuit breaker, some of the arc gases are reflected off walls of the circuit breaker housing, which slows arc transfer from the contacts to the arc chute and reduces the discharge rate of arc gases from the circuit breaker. Limitations on venting of the arc gases can raise the internal pressure beyond the limits of the breaker housing, thereby restricting the current interruption capability of the breaker. Venting of the arc gases has been hindered by the location of terminals through which the main conductors of the circuit breaker are connected to external conductors of the distribution system for which the circuit breaker provides protection.
There is a need therefore for an improved circuit breaker and a terminal assembly therefor that enhances the rate of discharge of arc gases to improve the current interruption capabilities of the circuit breaker.